name redacted wrote:Chevrolet's Sprint was a 3 cylinder normally aspirated econobox that routinely saw 35 mpg. And that was 80's technology.

Premium fuel is blended with ethanol (among other things) to achieve higher octane. Premium fuel with ethanol has less energy than unblended fuel. So the net result from fuel blended with ethanol is less MPG. Premium fuel does not give a noticeable increase in mileage despite what anyone thinks or says.

Every oil company uses different ratios of various chemicals to make their premium grade fuel. You will actually get different mileage results between manufacturers, than between one manufacturers regular/premium blends.

I got the best performance out of my spec miata racecar with Sunoco 87 octane pump swill, but my 409 big block Impala needs a minimum of 100 octane fuel. VP-C12 was ideal because it came in 100/110 octane, and had lead. But lead is no longer available in any fuel, race or otherwise, in the US.

When I raced GP motorcycles, it was basically an open class. Which meant that other than displacement, pretty much anything was allowed. So I experimented with many fuels. Some cost upward of $20 a gallon, and this was in 2003. VP-C12 was the best fuel for the dollar, at about $6.50/gallon. We would also blend some proplyene oxide to further increase its potential, but not being a chemist, I was reluctant to really fuck around with it. Plus it was $60 a gallon.

I had a supercharged Suzuki GSX-R with a roots type blower, that was run at a1:1 ratio. An NHRA guy I knew had some nitro benzyne he ran in his drag car. I added some to my fuel, and jesus christ, the difference was amazing. But god that shit is toxic as hell...

Interesting, the line
"Premium fuel does not give a noticeable increase in mileage despite what anyone thinks or says."
Then you proceed to chapter and verse on ways higher energy fuel does matter.
The specific answer is that premium matters if your engine can take advantage of it, as you obviously know already.
Power and efficiency are two sides of the same thing.

Spark tuning is a shortcut, but can matter, especially with an engine built for high octane in the first place.

For the average person, the thing to do is test the fuels.
Owner's manuals should say, but sometimes they don't want buyers put off by fuel requirements, so they leave it out.
Run a car long enough on your normal fuel to get a baseline, then try it with a premium fuel.
Then run the numbers.
It doesn't take a big mileage increase to save money buying premium.
That's what I did with the Fiat, before spark tuning.
With the distributor advance, it flat wouldn't run without premium, and it did matter to mileage.
Of course, we did it for power.

I had a friend with a Jag, and he absolutely would not run premium in it, even though he obviously would have saved money.
People are just crazy that way sometimes.

Re: benzene danger
There is a famous memo from 1958, exposed in a lawsuit.
It was sent to the President of Shell, I think.

"It has become clear that the safe exposure to benzene is 0 parts per million."

Chemists I know at Sunoco are convinced some of their friends died from benzene exposure.
However, untested chemicals don't have the research done, and may be as bad or worse.
I still have a container of nitromethane somewhere.

Nitropropane is an option that mixes better than nitromethane with diesel and gas.

BBurner, my Fiat was not all that slow, for a small engine.
There were many cars with better mileage, but very slow.
I think the best mileage tested then, at high speed, was the light weight Europa with the fairly low drag body, and well tuned engine.

This belongs in the car thread, but hey it's the bar, all topics are fair. I'm gonna try to put it in terms you don't have to be a total gearhead to read.
There's a lot of misunderstanding and outright misinformation about octane ratings and "premium" fuels.
"Premium" or higher octane gas has no more energy or power potential. Octane is merely the measure of how much it can be compressed before it self-ignites.
Higher compression in an engine will generally yield more power and efficiency, and that in turn requires gas that can be compressed more without igniting until the ignition system tells it to (fires the spark plug).
If you don't need premium you're doing nothing but throwing money away.

Modern electronic engine management systems make it a little harder to tell what's going on because the knock sensor (which senses when the fuel is pre-igniting from compression rather than igniting when the spark plug fires) signals the computer to retard the spark advance - which stops the preignition but also reduces power and efficiency, but it's automatic and seamless. You can't tell when it's doing it, you pretty much just have to experiment and see what octane rating your car makes the best MPG with.

GreyCoyote: "At this rate it wont be long before he is Admiral Fukkit."

Octane is primarily a measurement of resistance to knock, which can allow the tuning to be pushed.
In the past, premium was nearly always higher energy.
With ethanol, who knows what you're getting.

I think smaller engines are most likely to benefit from premium, but it varies.
My 318 van got better mileage on premium stock.
It was 2-3 mpg improvement.
I did a cost/benefit analysis and as long as premium wasn't marked up, as it is some places, it was cheaper to run premium.
Most of the time I ran a mix of high and low octane.

If there is a chance of premium saving you money, it's worth checking.

Hey guys, I see your mouths moving but all I hear is. "Hey the SF Decom is tomorrow. How many days till the man burns? Can you pass that platter of Poo-poos over here? Mmmmmm. Tofu Fingers. Did you watch that game last night? What? 15 innings! Does it seem like everyone is sick this month? Does this hat make my butt look big? My son's cat died of old age. Mine too! Let's drink to that.".

Have a great week-end everybody.

Those aren't buttermilk biscuits I'm lying on Savannah

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Talent hits a target no one else can hit; Genius hits a target no one else can see.Arthur Schopenhauer

The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

name redacted wrote: Lead is no longer available in any fuel, race or otherwise, in the US.

Just a quick point of correction: Leaded fuels are still manufactured and distributed in massive amounts in the USA. You need look only as far as your local airport. 100 octane "low lead" avgas contains more than TWICE the levels of tetraethyl lead in the old "high-test" automotive fuelds in the 1970s. And this stuff works very well in most engines designed to handle leaded fuel. The only downside is the flamefront propagation is a little too slow for 8000+ rpm engines to make their best power unless you add something to modify tthis part of the curve. Of course the downside is the cost: abiut $6 a gallon. Ouch.

"To sum up my compassion level, I think we should feed the unwanted animals to the homeless. Or visa versa. Too much attention and money is spent on both."(A Beautiful Mind)